Fluid pressure brake



Aug. 22, 1939. c.'c. FARMER 2,170,239

' FLUID PRESSURE BRAKE Filed May 17, '.1958

`INVENTOR ELYDE E. FARMER ATTORN EY Patented Aug. 22, 1939 UNITED STATES YPATENT OFFICE FLUID PRESSUREVBRAKE Application May 17, 1938, Serial No. .208,402l

18 Claims.

This invention relates to fluid pressure brakes, and more particularly to a brake apparatus operative to effect the building up of a high fluid pressure in the brake cylinder for causingl the 5 desired degree of application of the brakes.

In certain classes of transportation service, vehicles of co-nsiderable weight are operated at high speeds, and accordingly must be equipped with air brake apparatus adapted `to eiect application of the brakes with suilicient force or power to insure safe control of the vehicles or train of cars. Because of limitations in the space available on trucks and bodies on some modern cars, however, it may be difficult to mount thereon brake cylinders large enough and brake rigging of suitable amplifying power to produce the desired braking force when operated by fluid under a standard or moderately high pressure. In such a case the desired high braking ratio may, nevertheless, be provided by employing brake equipment including brake cylinders of suitable standard size but adapted to be supplied with fluid at a maximum pressure greater than the iluid pressure which would be required for larger and more V bulky brake cylinders having pistons of extremely large area.

One object of my invention is to provide an improved iluid pressure brake equipment adapted for economical and eicient service under the above conditions and including means operable to supply fluid at the desired high pressure to the brake cylinder without requiring the relatively Vdiflicult and expensive maintenance of unduly large supply volumes of fluid under maximum pressure.

In order to effect economical operation of suchY a fluid pressure brake equipment with a minimum volume of fluid maintained at extremely high pressure, it is desirable to provide vbrake controlling means adapted to respond to variations in pressure in the system charged with fluid under moderate or usual pressure, which might be seventy pounds per square inch, and operable thereby to effect ultimately the supply to the brake cylinders of liluid at a higher pressure, perhaps two hundred pounds per square inch, from a separately charged source.

it is another object of my invention to provide a fluid pressure brake equipment operable according to variations in the pressure of fluid maintained in a control system at moderate pressure to effect an initial supply of fluid from a primary source to the brake cylinder until the pressures are substantially equalized, and then operative i simultaneously to cut off communication between that source and the brake cylinder and to effect iinal supply of fluidfV under maximum pressure lfrom a separate source to the brake cylinder, thereby building up brake cylinder pressure to the desired degree with the relatively small volumeof fluid at maximum pressure required after the brake cylinder pressurer has been equalized Vwith that of the primary source.

A further object of the invention is to provide a iluid pressure brake equipment comprising means for maintaining a primary supply of fluid under moderate pressure and a supplementary supply of fluid under higher pressure, together with relay and control valve means automatically operative by fluid pressure to effect supply of fluid under pressure to the brake cylinder first from the primary source 'and then from the supplementary source.

Other objects and advantages of the invention will appear in the following detailed description f thereof, taken with reference to the accompanying drawing, wherein Fig. 1 is a diagrammatic View, partly in section, of a fluid pressure brake equipment embodying my invention; and Figs 2 and 3 are diagrammatic s sectional views of different forms of control valve devices which may be substituted for the control valve device illustrated in Fig. 1.

Description of embodiment shown in Fig. 1

The fluid pressure brake equipment illustrated in elementary form in Fig. 1 has the character- Vistics of a straight air brake system, but it should be understood that my invention is also adapted to be embodied in a brake system of the well g known automatic type in which a normally charged brake pipe is employed.

The simplified straight air brake equipment illustrated in Fig. 1 comprises a self -lapping brake lvalve device 5, a main reservoir 6, an auxiliary,

compressor l, a supplementary high pressure reskervoir 8, a brake cylinder 9, a differential relay valvedevice I0 and aV control or selector valve device Il. The equipment shown is adapted to be carried on a locomotive, but may of course be2 associated with other brake equipments including the brake cylinder and relay and control valves I0 and YI I carried on the cars coupled to the locomotive. The main reservoir 6 on the locomotive is adapted to be supplied in the usual manner, by a, suitable compressor, notshown, with fluid under a moderate or relatively low pressure, which may be seventy pounds per square inch, and vis connected to a low pressure supply pipe I4 extending throughout the train'. The auxiliary compressor 'I is operative to supply fluid to the high pressure reservoir 8 at a pressure considerably in excess of the normal pressure of fluid maintained in the main reservoir 6. Fluid may thus be maintained in the supplementary high pressure reservoir 8 at about two hundred pounds per square inch, and is supplied therefrom to the high pressure supply pipe I5, which like the low pressure supply pipe I4 extends throughout the train. Y

According to my invention, the differential relay valve device I0 comprises a casing section I6 having a chamber Il, a cover plate 20 mounted on the casing section I6, and an'in-terposed casing section I8, the three casing members being secured together by any suitable means such as bolts, not shown. The chamber I'I communicates by Way of a passage and pipe I9 with the brake cylinder 9. Interposed between the casing section I8 and cover plate 2@ is a flexible diaphragm 22, which together with the cover plate 20 dein'es a chamber 23 communicating with an operating or straight air pipe 24 that extends throughout the train. Interposed between the casing sections mand i6 is a exible diaphragm 26, the pressure area of which is considerably less than that of the diaphragm 22. The diaphragm 23 is subject to the pressure of fluid in the chamber I'l and is operatively connected to the larger diaphragm 22 by means of a follower element 21, which is disposed in a chamber 28 formed intermediate the two diaphragmsand communicating with the atmosphere.

The associated diaphragms 22 and 2t are designed to operate a supply and release valve actuating mechanism, which is mounted in the casing I6 and is similar to that employed inthe relay valve device disclosed in the United States Patent 2,096,491 issued on October 19, 1937, to E. E. Hewitt. This mechanism includes a plunger 33, which is slidably mounted in a suitable bore formed in a portion Ital of the casing section IB and is urged into operative engagement with a follower 32, carried on the diaphragm 36, by a spring 3l interposed between portion Ia and a shoulder 330i the plunger 30, and a lever 39 which is pivotally mounted intermediate the'ends thereof on the plunger 30. The lever 39 is arranged to operate. a supply valve 34 and pilot valve 35 having a stem 35 operatively aligned with one end 3i of the lever, and a release valve 43 and its pilot valve 38 operatively connected by means of a stem 4I to the other end 42 of the lever.

The supply valve 34, which is mounted in a bore 44 formed in the casing section I6, is urged toward seated position by a spring 45 which is interposed between the valve and a cap nut 46, and the pilot valve 35 is urged toward seated engagement with a suitable seat formed on the supply valve 34 by a similarly mounted spring 49. The supply valve 34 and its pilot valve 35 are cooperative tol control communication from a supply pipe and passage 5i! to the chamber Il, as will be hereinafter explained.

The release valve 4t has a piston portion 53 slidably mounted in a bore 54 formed in the casing, and is adapted to control communication between the chamber I'I and an atmosp-heric exhaust port 55. The pilot valve 38 associated with the discharge valve 4I) is adapted to establish equalization of the opposing fluid pressures on the valve 40 and piston portion 53 for facilitating unseating operation of the valve through the medium of the stem 4I.

According to the invention, the control or selector valve device I I is operative selectively to control communication from either the low pressure supply pipe I4 or the high pressure supply pipe I5 to the inlet passage 50 of relay valve device I0, As shown in Fig. l of the drawing the control valve device II comprises a casing 6) having formed Itherein a valve chamber 6I containing a slide valve 62, which is adapted to be operated by a piston S3 through the medium of a stem 64. The piston 63 is subject on one side to the pressure of uid in the valve chamber 3l and on the opposite side to the combined pressures of fluid in a chamber 65, connected through the pipe I9 with the brake cylinder 9, and of a spring 36, which is interposed between the piston and a cap nut 6l secured to the casing.

The valve chamber B! is always in communication through a passage Ilia with the low pressure supply pipe I4, and, with the slide valve 62 in the normal or low pressure supply position as vshown in Fig. 1,'the' valve chamber also communicates by way of a port 59 in the slide valve lseat with the pipe Ell, which leads to the relay valve device II). The slide valve 32 has a cavity 'ID formed therein, which cavity is adapted on movement of the slide valve to a high pressure supply position, as hereinafter explained, to establish communication between the port 69 and `a port 'El which is connected to the high pressure supply pipe I5.

Means is provided for loading the slide valve 62, which means comprises a substantially vertically disposed rod i3, the lower end of which operatively engages in a suitable recess in the slide valve E52 and the upper end of which is secured to a flexible diaphragm 14 clamped between the casing 6i) and a cover plate 75. For urging the diaphragm I4 and rod 'I3 downwardly, a spring 'I'I is interposed between the rod and the cover plate 'i5 within a chamber i3, which communicates by way of a passage "I9 with the high pressure supply pipe I5.

Operation of embodiment shown in Fig. 1

With the self-lapping brake valve device 5 in release position, the chamber 23 of the relay valve device I3 is connected with the atmosphere by way of the pipe 24 and suitable ports, not shown, in the brake valve device, so that the valve mechanism in the relay valve device is permitted to assume release position. In this position of the relay valve devicey the spring 3| is adapted to maintain the plunger 3E! in its extreme left-hand position asviewed in the drawing, the end 3l of the lever 39 being thereby positioned in engagement vwith a stationary abutment 83 carried by the portion Ita of the casing, so that the lever 39 is urged in a clockwise direction about its pivotal connection with the plunger for causing the end 42 toY hold the pilot valve 38 and exhaust valve 4B in unseated position, through the medium of thestem 4I. The supply valve 34 and pilot valve 35 are at the same time maintained in seated position by the springs 45 and 49 respectively. With the relay valve device I@ in release position, the brake cylinder 9 is thus connected with the atmosphere 'by way of the pipe and passage I9, chamber I'I, and past the unseated exhaust valve 40.

The main reservoir 6 is charged in the usual manner with fluid under a moderate or relatively low pressure, and a portion of the fluid under pressure from the main reservoir is, as already explained, supplied under the desired high pressure to the high pressure reservoir by operation of the auxiliary compressor 1. Fluid under pressure is also supplied from the main reservoir 6 by way of the low pressure supply pipe I4 to the valve chamber 6I of the control valve device II, and since the chamber 65 on the opposite side of the piston 63 is at this time connected to the atmosphere together with the brake cylinder 9, the fluid pressure acting in the valve chamber 6I forces the piston into the position shown in Fig. l of the drawing, against the force of the spring 66, the slide valve 62 being thereby positioned to close the port 1I while maintaining communication from the chamber 6I through the port 69 and pipe 50.

If it is desired to effect an application of the brakes, the engineers brak valve device is moved to a position within the application zone, and the self-lapping valve mechanism therein is thereby operated in the well known manner to effect supply of fluid under pressure from the main reservoir 6 through the straight air pipe 24 to the diaphragm chamber 23 of the differential relay valve device I0. The pressure of fluid thus supplied to the chamber 23 acts against the diaphragm 22 to shift the follower member 21, diaphragm 26, follower member 22 and plunger 30 toward the right as viewed in the drawing, against the pressure of the spring 3l. The end 31 of the lever 39 is at this time fulcrumed on the end of the pilot valve stem 36, which is held against movement by the pressure of the spring 49, so that initial movement of the plunger 30 causes the lever 33 to be tilted in a counterclockwise direction, the end 42 thereof being thus operated to move first the pilot valve 38 and. then the release valve 40 to their seated positions for cutting off communication between the chamber I1 and the atmosphere.

The end 42 of the lever 43 is then fulcrumed on the stem 4I, and continued movement of the plunger 30 under the force of fluid acting against the diaphragm 22 thereupon effects tilting of the lever in a clockwise direction, the end 31 thereof moving the stem 36 to unseat the pilot valve 35. With the pilot valve unseated, the fluid pressure on opposite sides of the supply valve 34 are substantially equalized, so that the supply valve is then readily unseated by further operation of the stem 36 against the force of the spring 45.

With the supply valve 34 thus unseated, fluid under pressure is supplied from the low pressure supply pipe I4 through the valve chamber 6I of the control valve device II, the port 69, pipe and passage 50, past the unseated valve 34, and through the chamber I1 of the relay valve device, and passage and pipe I9, to the brake cylinder 9, for effecting an :application of the brakes.

At the same time, iluid under pressure is supplied by way of the brake cylinder pipe I9 to the chamber 65 of the control valve device II. Assuming that the handle of the brake valve device 5 has been moved far enough to effect a fairly heavy application of the brakes, so that the force exerted by fluid under pressure in chamber 23 of the relay valve device acting on the large diaphragm 22 remains greater than the force exerted against the small diaphragm 26 by fluid supplied Afrom the low pressure supply pipe- I4 as just described, the relay valve device I0 is maintained in application position for continuing supply of uid under pressure from the low pressure supply pipe to the brake cylinder 9 and chamber 65 of the control valve device II. As

the pressure of fluid thus supplied to the chamber 65 approaches equalization with the fluid pressure acting in the valve chamber 6I against the piston 63, the spring 66 becomes eective to shift the piston 63 and thereby the slide valve 62 to the left as viewed in the drawing, until the cavity of the slide valve registers with the port 69. With the slide valve 62 so positioned, communication between the valve chamber 6I and the port 69 is thus cut olf while communication is established through which fluid under high pressure is supplied from the high pressure reservoir 8 and supply pipe I5 by way of the port 1I, cavity 16, port 69, pipe and passage 50, past the still unseated supply valve 34 in the relay valve devi-ce I0, and thence through the chamber I1 and passage and pipe I9 to the brake cylinder 9, which is thereby operated to effect application of the brakes with the desired high braking force.

Fluid under high pressure is thus supplied from the high pressure reservoir 8 to the brake cylinder 9 until the uid pressure in the chamber I1 of the relay valve device IU and acting against the small diaphragm 26 is increased sufilciently to equal the opposing pressure of fluid in the chamber 23 acting on the large diaphragm 22. When the fluid pressure in the chamber I1 reaches such a value, the diaphragme 26 and 22 are moved to the left, under the force of the spring 3I acting on the plunger 30 and of the springs 45 and 49 acting on the supply valve 34, the force of the latter springs being transmitted through the medium of the stem 36 and lever 39 to the plunger 30. The lever 39 is then tilted in a counterclock- Wise direction about its pivotal connection with the plunger for permitting engagement of the valve 34 with its seat while maintaining the exhaust valve 40 seated. With further supply of' fluid under pressure to the chamber I1 and the connected brake cylinder 9 thus cut off, the parts of the relay valve device I0 are consequently held in lap position.

In order to effect the release of the brakes following a high pressure application as just described, the engineer moves the handle of the brake valve device 5 to release position, whereby the straight air pipe 24 is again connected to the atmosphere for releasing fluid under pressure from the chamber 23 of the relay valve device IIJ. Upon reduction in the pressure of fluid in chamber 23, the fluid pressure in the chamber I1 becomes effective to move the diaphragm 26, follower member 21 and diaphragm 22 to release position as shown in Fig. 1. At the same time, the spring 3| operates the plunger 35 and lever 39 of the valve mechanism to effect unseating of the pilot valve 38 and exhaust valve 40, so that fluid under pressure is quickly vented from the brake cylinder 9 and chamber 65 of the control valve device II by way of the pipe and passage I9, the chamber I1 of the relay valve device, and past the unseated valve and through the exhaust passage 55, thereby effecting the release of the brakes.

As the pressure of fluid in the chamber 65 of the control valve device II is thus reduced, the spring 66 is caused to yield under the force of fluid in the valve chamber 6I acting against the piston 63, and the piston is thereby operated to ymove the slide valve 62 toward the right into the position shown in Fig. l, this movement of the slide valve cutting off communication be- .tween the port 1I and port 69, while establishing communication from the chamber 6I to the port69.

It will be apparent that, since the equipment just described is thus operative first to supply uid from a low pressure source to the brake cylinder until the fluid pressure therein is substantially equalized with that in the low pressure source, and then to cut olf the low pressure source and to eifect further supply of fluid from a high pressure source for building up maximum brake cylinder pressure, the quantity of fluid which must be maintained under high pressure in the high pressure source is considerably less than would be the case if the brake cylinder were to be supplied only from the high pressure source. It will also be evident that, for a required maximum brake cylinder pressure, the pressure of fluid with which the high pressure source is charged may be lower, and consequently more economically maintained, than would be necessary if the fluid pressure in the high pressure source were equalized with both the brake cylinder pressure and that of the low pressure source.

Description of embodiment shown in Fig. 2

Another form of control valve device constructed according to the invention is illustrated in Fig. 2 of the drawing, this control valve device, which is indicated generally by the character Ia, being adapted to perform functions similar to those already explained in` connection with the control valve device II shown in Fig. l. It will thus be understood that the control Valve device I Ia. may be substituted for the control Valve device I I in association with the equipment shown in Fig. 1.

Referring to Fig. 2 of the drawing, the control Valve device IIal comprises casing sections 80, 8| and 82, the latter two casing sections being secured to the casing section 89 by any suitable means, such as bolts, not shown. The casing section 89 has formed therein a valve chamber 84 communicating through a passage 85 with the high pressure supply pipe I5, a valve chamber 88 communicating through a passage 8l with the low pressure supply pipe I4, and a chamber 89 which is disposed intermediate the valve chambers and communicates with the pipe 50. Disposed in the valve chamber 88 is a valve 9|, which is adapted to control communication between the chamber at and the chamber 89 and is normally urged into engagement with a seat 92 by the force of a spring 93, which is interposed between. the valve and a cap nut 9d. having screwthreaded engagement with the casing section 89 for closing the chamber 88. A uted stem 95 of the valve 9i extends into the chamber 89 and is adapted to engage a similar iluted stern el of a valve 99, which is disposed in the valve chamber 85. The valve 9E! is engageable with a seat 99 and is adapted to control communication between thc chambers 86 and 88, it being noted that the valve 98 is held in unseated position while the Valve 9i is in seated position as shown in Fig. 2.

For operating the associated valves 9| and 98, there is provided a piston Ibi, which is slidably mounted in a suitable bore formed in the casing section 8E and has a stem i112 disposed in operative alignment with a plunger |03 which is in turn operatively aligned with the valve 98. The plunger |02 and plunger |83 are slidably mounted in a bore i08- formed in the casing section 8|. A yielding or lost motion connection is provided between the piston IOI and the valve'98 by means of a coil spring |06, which is interposed between the valve 98 and a follower |07 carried on the end of the plunger |03, and a similar coilspring |08 which is interposed between the plunger |03 and the stem |02 of the piston. The piston |0I has formed at one side thereof a chamber IIO communicating by way of a passage I I I with the atmosphere, and is subject on the opposite side to the pressure of fluid in. a chamber II2 communicating with a passage II3 formed in the casing.

The piston IOI is normally urged toward the right hand into the position shown in the drawing by the force of the spring 93 transmitted through the valves 9| and 98, spring |06, plunger |93, spring |08 and the stem |92. It will be noted that the member |01 is adapted to seal against a gasket IIII when the associated elements of the control valve device IIw are in the position shown in Fig. 2, so that leakage from the chamber 85 by way of the bore |04 and charnber IIO is prevented. For the same purpose the plunger |03 is provided with an inclined shoulder I i which is adapted to engage a seat I I6 formed within the casing section 8| upon movement of the plunger |03 to the left by the piston IOI, as hereinafter explained.

Slidably mounted in aV suitable bore formed in the casing section 82 is a piston valve III, having a face IIB normally urgedV into engagement with an annular seat rib |20, formed on the casing at one end of the bore, by the force of the spring I2I, which is disposed in a chamber |22 between` the valve III and a member |23 adjustably secured to the casing. The annular seat rib |29 defines a central chamber |25 which is connected with the brake cylinder pipe I9, and also defines a chamber |26 surrounding said seat rib, so that fluid under pressure supplied through the pipe I8 acts initially on the inner seated area of the piston valve II'I exposed to the chamber |25 until the piston valve is unseated, whereupon the entire area of the valve will be exposed to the fluid pressure. The piston Valvev II'I is thus adapted to'be moved from seated position to unseated position with a sol-called snap action.

With the piston valve IIl in seated position as shown in Fig. 2, the passage IIS leading from the piston chamber II2 communicates with the atmosphere through the spring chamber |22 and a passage |29 formed in the member |23. Upon movement of the piston valve II'I to unseated position against the force of the spring I2I as hereinafter explained, communication between the passage IIS and the chamber |22 is cut off, and the valve at the same time uncovers a port 35 for establishing communication between the passage II3 and the chambers |26 and |25.

Operation of embodiment shown` in Fig. 2

1n order to effect an application of the brakes, the engineer operates the brake valve device for effecting operation of the differential relay valve device to initiate the supply of fluid under pressure to the brake cylinder in the manner hereinbefore described in connection with the rst embodiment of the invention, it being understood, by reference toV both Figs. l and 2 of the drawing, that iuid from the low pressure supply pipe I4 is thus supplied through the passage 8l of the control valve device IIa, the chamber 86, past the unseated valve 98, through the chamber 89 and pipe 5I) which communicates with the relay valve device, and thence to the brake cylinder which communicates with the pipe I9.

When the pressure of iiuid thus supplied from the low pressure supply pipe I5 to the brake cylinder pipe I9'V and the chamber |25 is increased 5"movement of the Valve until the valve 98 en- Vfthe spring |98, which is heavier than either of cured tothe casing section I 4I.

" passage sufliciently to cause unseating'of the piston valve ||1 against the predetermined force of spring I2I, the piston valve is quickly moved to its uppermost position, as viewed in Fig. 2, and fluid at brake cylinder pressure is then supplied from the pipe I9 through the chambers |25 and |26, port |30 and passage |I3 to the chamber ||2. 'I'he pistonIlI is thereby shifted inwardly or to the left, referring to Fig. 2, and in so moving acts through the medium of the stem |02, spring |08, plunger |03 and spring |06 for moving the associated Valves 98 and 9| to Seated and unseated positions, respectively. It should be un-` derstood that the spring 93 which acts, on the Valve 9| is adapted to yield during the above gages the seat 99, whereupon the somewhat stronger spring |06 is compressed suiliciently to permit engagement of the shoulder ||5 of the plunger |03 with the seat ||6 under thesforce of the springs Y93 and |06.

With the valve 98 seatedY and the valve `9| un-V seated, communication is established for the sup ply to the brake cylinder of fluid under high "pressure, which flows from the Vhigh pressure supply pipe I5 through the valve chamber 84 and past the unseated valve 9|, through the chamber 89 and pipe 50 to the relay valve device, and `thence as already explained to the brake cylinder lfor building up the desired brake cylinder pres- Sure.

In effecting the release of the brakes, uicl under pressure is vented from the brake cylinder,V Yand consequently from the pipe I 9, in the manner hereinbefore explained, Upon the reduction in the pressure of fluid acting on the piston valve Ill, the spring I2I becomes effective to move`4 the valve to seatedv position, the `passage I |3 being thereby connected through chamber |22 and |29 with the atmosphere.' vThe uid pressure in the piston chamber ||2 is thus reduced, so that the spring 93- is permitted to return the valves 9| and 98 Yand the movable elements including the piston I|JI associated therewith to the normal position shown in Fig. 2 of the drawing. Y

Description of embodiment shown in Fig. 3 In Fig. 3 of the drawing my invention is shown embodiedin a control valve device IIb, which comprises a pipey bracket'fIMl` havingsuitably secured thereto casing sections 1|4I, |42 and |43. Formed in the casing section |4| is a valvechamber |44 communicating by. way of a passage|45 with the high pressure supplypipeY I5 andcontaining a slide Valve |46., which is operatively connected through the medium of a stem |41 with a piston |48 that is slidably mounted in a suitable bore formed in the casing. The piston 4-`|48 is subject on one side to the pressure of uid in the valve chamber |44,and has at the opposite side a chamber |50, which communicates with a passage I5I. A biasing spring |52 is disposed between the piston |48 and a coverplate |53 sein, Disposed inthe valve chamber |51 is a valve |62v having a flutfed stem |63 which extends through a suitable bore into the chamber |55 and in operative alignment with the stem |60. Interposed between the valve |62 and a cap nut |65 is a coil spring |66 which acts normally to maintain the valve |62 in seated position while holding the valve |59 in unseated position, as shown in the drawing. n

Means for actuating the associatedvalves |59 and |62 is provided in the casing section |42, comprising a valve piston |10 slidably mounted in a suitable bore formed in the casing and having' at one side thereof a chamber |1| surrounding an annular seat rib |12, which rib is engageable by the valve piston |10 and together With the piston defines a chamber |13 communicating with the brake cylinder pipe I9. The valve piston |10 is urged into engagement with the seat rib |12 by the force of a spring |14, which is disposed in a chamber |15 that communicates with the atmosphere through a passage |16. In order to transmit movement of the valve piston |10 away from the seat rib there is provided a plunger 11, which is slidably mounted in a suitable bore in the casing and has one end thereof disposed in operative alignment with the end of a projecting stem |18 of the valve |59, the opposite end of the plunger |11 extending into the chamber |15 and having formed thereon a collary |19, which rests-on a spring |80 carried by the valve piston |10.

Operation of embodiment shown in Fig. 3 With the brake equipment including the control valve device shown in Fig. 3 in release position, it will be understood that the brake cylinder pipe I9 together with the brakev cylinder, not shown in Fig. 3, is connected with the atmosphere, so

that the Valve piston |10, being subject only to f atmospheric pressure, is maintained in engagement with the seat rib |12 as shown by the force of the spring |14. With the valve piston |10 in its lowermost position, the plunger |11 is positioned out of operative engagement with the stem |18, and the spring |66 is thus permitted to maintain the valve |62 seated, while the valve I 59 is inunseated position. With the valve |59 in unseated position, the chamber |50 at the I f outer face o-f theA pistonV |48v is connected with the atmosphere by Way ofthe passage |5I, chamberl55, past the fluted stem |60 and vunseated valve |59, and through the chamber |56 and passage |58. At the same time, fluid from the high pressure supply pipe- I5 is supplied through the passage tothe slide'valve chamber |44 and acts on' the piston |48 in opposition to the force of the spring |52 for maintaining fthe piston, stem |41 thereof, and slide valve |46 in the normal position shown in Fig. 3, in Which position communication is maintained from the low pressure supply pipe I4 through a passage |82, a cavity |83 formedin the slide valve, and Y a passage |84 with the pipe 50, which of course leads to the seat of the supply Valve in the difierential relay valve device as shown in Fig. 1 of the drawing.

In operation, an application of the brakes is initiated when they equipment is operated in the manner already explained to effect supply of fluid from rthe low pressure supply pipe I4 by Way of communications in the control Valve device IIb and through pipe 50,110 the brake cylinder pipe I9, the fluid pressure in the brake cylinder andr vin ,the' chamber |13 communicating With the brake cylinder pipe `being then built up to substantially the pressure of equali- Zation of pressure in the pipe I4 with that in the brake cylinder. Upon this predetermined increase in fluid pressure in the chamber |13, the valve piston |13 is forced upwardly and away from the seat rib |12 against the pressure of the spring |14. As the valve piston is thus unseated, brake cylinder pressure acts on the area thereof exposed to the chamber |1| and quickly shifts the piston to its uppermost position, the spring We and the plunger |11 being thereby operated to move the valve |59 into seated position while unseating the valve |62.

With the valve |59 seated, communication to the atmosphere from the chamber |55 isv out off, while communication is established between the chambers |51 and |55 so that fluid at high pressure is supplied from the chamber |44 through passage |455, valve chamber |51, chamber |55, and passage l5| to the chamber |56. The fluid pressures acting on opposite sides of the piston |48 are thus equalized, whereupon the spring |52v becomes effective to shift the piston |48, stem |41 and slide valve Ille to the left as viewed in they drawing, the slide valve being thereby operated to cut off communication between the low pressure supply pipe lll and the passage |84, while establishing communication to that passage from the valve chamber IM.l The supply of iiuid under pressure to the brake cylinderl is thereafter continued by flow of fluid from the high pressure supply pipe l5 through the passage |45, chamber Hill, passage |34 and pipe 5e until the desired brake cylinder pressure is attained.

It will now be apparent that my invention, employed in any of the several illustrative embodiments just described, is operative in effecting an application of the brakes to supply fluid under pressure to the brake` cylinder first from a moderate or relatively low pressure source of supply until a predetermined brake cylinder pressure it attained, and then from a high pressure supply source, thereby providing a desired high brake cylinder pressure with maximum efciency and economy in the use of fluid.

Although three embodiments of my invention have been described in detail, it should be understood that I do not intend to limit the invention to those embodiments or otherwise than by the terms of the appended claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

l., In a` fluid pressure brake apparatus, in com.- bination, aY brakecylinder, a relay valve device operable to supply fluid under pressure to said brake cylinder for effecting an application of the brakes, control valve means controlling the communication through which` said relay valve device supplies: fluid to said brake cylinder, and means normally conditioning said. control valve means to permit supply of fluid at moderate pressure through said communication and operative upon a predetermined increase in. brake cylinder pressure to condi-tion said control valve means to permit supply through said communication to said brake cylinder of fluid at a` higher pressure.

2. In a fluid pressure brake equipment, in combination, a brake cylinder, a source of supply of fluid under low pressure, a source of supply of fluid under high pressure, a relay valve device controlling the supply of fluid from either of said sources to said brake cylinder for effecting an application of the brakes, brake valve means operable to control supply of iiuid from said. low pressure supply source to said relay valve device in accorda-nce with a desired degree of braking, and a control valve device operative when the pressure of uid in. said brake cylinder is below a predetermined value for permitting supply by said relay valve device of fluid from said low pressure source to the brake cylinder, and operative when the pressure of fluid in the brake cylinder is above said predetermined value to permit suxpply of fluid by said relay valve device only from the high pressure source to said brake. cylinder.

3. In a. iiuid pressure brake equipment, in combination, a brake cylinder, a primary source of fluid under a certain pressure, a supplementary source of uid under a higherl pressure, brake controlling apparatus including a relay valve device operable to supply fluid Linder pressure from either of said sources to said brake cylinder for effecting an application of the brakes, and valve means normally positioned to provide communication from said primary source of fluid under pressure to said relay valve device and operative upon a predetermined increase in brake cylinder pressure to establish communication from said supplementary source of iiuid under pressure to said relay valve device.`

4. In a fluid pressure brake apparatus, in combination, a brake cylinder, a primary source of fluid under a certain pressure, a supplementary source of iiuid under a higher pressure, brake controlling apparatus including a relay valve device operable to supply fluid under pressure from either of said sources to said brake cylinder, and a valve device controlling the communication through which said relay valve device is adapted to supply fluid, said valve device being normally adapted to pro-vide communication. from said primary source of fluid under pressure to said relay valve device and operative upon av predetermined increase in brake cylinder pressure to cut oif the communication from said primary source and to establish communication from said supplementary source to said relay valve device.

5. In a vehicle carried fluid pressure brake, the combination with a brake cylinder and brake controlling valve means of the graduating type for controlling the supply and release of fluid under pressure to and from said brake cylinder,

of a plurality of sources. of supply of fluid under' pressure, and uid supply selector means operative, in accordance with variations in the pressure of fluid in said brake cylinder, to render said controlling valve means eiective in operation to supply fluid; under pressure from said supply sourcesy to said brake cylinder in succession.

6. In a vehicle carried fluid pressure brake, the combination With a brake cylinder and a brake controlling valve device of the graduating type for` controlling the supply and release of fluid under pressure to and from said brake cylinder, of a source of fluid under low pressure, a source of fluid. under high pressure, and iiuid supply selector means responsive to the pressure of fluid in said brake cylinder, said supply selector means being operative when brake cylinder pressure is less than. al predetermined value to render said controlling valve device effective in operation, to sup-ply fluid under pressure to said brake cylinder from said low pressure supply source, and when brake cylinder pressure exceeds said predetermined value to render said controlling valve device effective to supply fluid to the brake cylinder from said high pressure source.

7 In affluid pressure-brake, in combination, an

operating pipe, a low pressure supply pipe, a high pressure supply pipe, a brake cylinder, a relay Valve device responsive to an increase in fluid pressure in said operating pipe to effect the supply of fluid under pressure from one or the other of said supply pipes to said brake. cylinder for causing an application of the brakes, brake control valve means operable to control the pressure of fluid in said operating pipe in accordance with the desired degree of brake application, and supply selector valve means operative in accordance with operation of the relay valve device for causing said device to supply fluid under pressure to said brake cylinder initially from said low pressure supply pipe, and then from said high pressure supply pipe.

8. In a fluid pressure brake, in combination, an operating pipe, a lovv pressure supply pipe, a high pressure supply pipe, a brake cylinder, a relay valve device responsive to an increase in fluid pressure in said operating pipe to effect the supply of fluid under pressure from one or the other of said supply pipes to said brake clinder for causing an application of the brakes,'brake control valve means operable to control the pressure of fluid in said operating pipe in accordance with the desired degree of brake application, selector valve means controlling the communications through which said relay valve device is: adapted to supply fluid from each of said supply pipes to said brake cylinder, and means for operating said selector valve means in accordance with brake cylinder pressure.

9. In a fluid pressure brake equipment, in combination, a brake cylinder, a low pressure supply pipe, a high pressure supply pipe, brake controlling valve means operable to control communications from either of said supply pipes to said brake cylinder in effecting an application of the lbrakes, selector valve means also controlling said communications, and means responsive to brake cylinder pressure for actuating said selector valve means, said selector valve means being normally conditioned thereby to permit supply by said controlling valve means of fluid under pressure from A'said loW pressure pipe to'said brake cylinder, and

operative upon a predetermined increase in brake cylinder pressure to cut off said communication from the lovv pressure pipe while establishing communication for continued supply of fluid by said controlling valve means from said high pressure pipe to said brake cylinder.

l0. In a fluid pressure brake, in combination, a source of fluid under low pressure, a source of fluid under high pressure, a brake cylinder, a fluid pressure operated relay valve device controlling the supply of fluid under pressure separately from each of said sources to the brake cylinder in effecting an application of the brakes, said relay valve device being actuated by fluid supplied thereto from said loW pressure source when an application ofthe brakes is initiated, and a control valve device responsive to brake cylinder pressure for also controlling the communication through which fluid under pressure is supplied to said brake cylinder, said control valve device being normally conditioned to provide communication from said low pressure source through said relay valve device to the brake cylinder and operative upon a predetermined increase in brake cylinder pressure to establish a different communication from said high pressure source through the relay valve device to said brake cylinder.

11. In a fluid pressure brake, in combination, a

source of `fluid under low' pressure, a source of fluid under high pressure, a brake cylinder, a relay valve device comprising a self-lapping valve mechanism controlling supply of fluid under pressure from either of said sources to the brake cylinder and a pair of associated diaphragms having different areas for actuating said mechanism, the smaller diaphragm being subject to brake cylinder pressure and the larger diaphragm to the opposing pressure of fluid supplied thereto from said lovv pressure source When an application of the brakesis initiated, and a control valve device controlling the communication through which said relay valve device is adapted to supply fluid under pressure to the brake cylinder, said control valve device being normally conditioned to permit supply of fluid from said low pressure source to the brake cylinder and operative upon a predetermined increase in fluid pressure in said brake cylinder to permit further supply of fluid thereto from said high pressure source.

12. In a fluid pressure brake, in combination, a brake cylinder, a source of fluid under loW pressure, a source of fluid under high pressure, brake controlling valve means operable to effect supply of fluid from either of said sources to said brake cylinder -for effecting an application of the brakes, and a valve device for selecting the source from which said brake controlling valve means is adapted to effect supply of fluid to the brake cylinder, comprising valve means subject to the pressure of fluid supplied to said brake cylinder and to a substantially constant opposing fluidy pressure, said valve means being normally adapted to maintain communication through Which fluid under pressure is supplied from said loW pressure source to the brake cylinder, and operative upon a predetermined increase in brake cylinder pressure to cut ofi said communication and to establish another communication throughy Which fluid under pressure may be supplied from said high pressure source to the brake cylinder.

13. In a fluid pressure brake equipment, in combination, a primary source of fluid under lovv pressure, a supplementary source of fluid under high pressure, a brake cylinder, brake controlling valve means operable to effect supply of fluid from either of said sources to said brake cylinder for effecting an application of the brakes, and a valve device for selecting the source from which said brake controlling valve means is adapted to effect supply of fluid to the brake cylinder, comprising a spring, a movable abutment subject to the opposing pressures of fluid from said primary source and of the spring plus the fluid pressure in said brake cylinder, and a Valve operative by said abutment for normally maintaining communication from said 10W pressure source to said brake controlling valve means and upon a predetermined increase in brake cylinder pressure for establishing communication from said supplementary source of fluid under pressure to said brake controlling valve means.

14. In a fluid pressure brake, in combination, a source of fluid under 10W pressure, a source of fluid under high pressure, a brake cylinder, and means controlling the supply of fluid from said sources to said brake cylinder in effecting an application of the brakes, said means including a control valve device comprising a slide valve normally positioned to maintain communication through which fluid under pressure may be supplied solely from said low pressure source to said brake cylinder, a movable abutment operative upon a predetermined increase in brake cylinder 75 pressure to move said slide valve to establish communication through which fluid is supplied solely from said high pressure source to said brake cylinder, and means for loading said slide valve under the pressure of uld from said high pressure source.

15. In a fluid pressure brake, in combination, a source of fluid under low pressure, asource of fluid under high pressure, a brake cylinder, and

'means controlling the supply of fluid from said sources to said brake cylinder in effecting an application of the brakes, said means including a control valve device comprising valve means normally positioned for maintaining communication through which fluid under pressure may be supplied from the low pressure source to the brake cylinder, a movable abutment operative upon the supply of fluid under pressure to a chamber to move said valve means to another position for .establishing communication through Which fluid under pressure may be supplied from said high pressure source to the brake cylinder, and fluid pressure actuated valve means responsive to a predetermined increase' in brake cylinder pressure for supplying fluid under pressure to said chamber.

i6. In a fluid pressure brake, in combination,V

establishing communication through which uid under pressure may be supplied from said high pressuresource to the brake cylinder, and a snapaction valve biased toward a normal position for venting said chamber to the atmosphere and operative upon a predetermined increase in pressure of fluid being supplied from said low pressure source to the brake cylinder for supplying a portion of said uid under pressure to said chamber.

17. In a fluid pressure brake, in combination, a source of fluid under low pressure, a source of fluid under high pressure, a brake cylinder, and brake controlling apparatus operable to effect the supply of iiuid under pressure from one or the other of said sources to said brake cylinder in effecting the application of the brakes, including fluid pressure responsive valve means having a normal position for maintaining communication through Which fluid under pressure is supplied from said low pressure source to the brake cylinder and movable to another position upon an increase in the pressure of fluid in a chamber for establishing communication through which fluid under pressure may be supplied from said high pressure source to said brake cylinder, and snapaction valve means responsive to a predetermined increase in brake cylinder pressure for supplying ud under pressure from said high pressure source to said chamber.

18. In a fluid pressure brake, in combination, a source of fluid under low pressure, a source of Y fluid under high pressure, aI brake cylinder, and

brake controlling apparatus operable to effect the supplyof fluid under pressure from one or the other of said sources to'said brake cylinder for effecting an application of the brakes, including fluid pressure responsive valve means having a normal position for maintaining communica.- tion through which fluid may be supplied from said low pressure source to said brake cylinder and movable to another position on an increase in the pressure of fluid in a chamber for establishing communication through which fluid may be supplied from said high pressure source to said brake cylinder, valve means normally connecting said chamber to the atmosphere, and a snap-action piston operative upon a predetermined increase in brake cylinder pressure to operate said valve means for supplying fluid under pressure to said chamber.`

CLYDE` C. FARMER. 

